New research finds the drug could cure depression in hours, but there's a hitch: This is the same drug used recreationally as 'special K', and its 'high' can include hallucinations.

The anesthetic drug ketamine — also used illegally as a party drug called "special K" — could be effective in almost instantly relieving some patients of depression, according to research published this month in the journal Science.

"It's exciting," said lead author Ronald Duman, a professor of neurobiology and pharmacology at Yale University, when he spoke with NPR. "The hope is that this new information about ketamine is really going to provide a whole array of new targets that can be developed that ultimately provide a much better way of treating depression." The study in Science is what's known as a review paper: it examines other published research on a subject to synthesize key findings. Duman called ketamine "maybe one of the biggest findings in the field [of treating depression] over the last 50 years."

Ketamine, under its approved FDA use, is a dissociative anesthetic for both humans and animals. When used illegally — usually after drying the veterinary version of the liquid into powdered form — it can create hallucinations and dream-like states, according to the website drugfree.org.

This is not Duman's only research related to ketamine. He told NPR he has also experimented with the drug on depressed mice. In that study, mice were exposed to stressful conditions that would cause the synaptic connections between the nerve cells in their brains to atrophy, much the same way human brains react to long periods of depression. The researchers gave ketamine to these mice and found that some of the synaptic connections were rapidly restored.

Duman told the Hartford Courant that the new research shows the connections in the brain are adaptable and changeable, unlike the previous understanding that they could not be changed. "Even though depression and stress are associated with a loss of those connections, these are reversible conditions. And that's a hopeful discovery," he said.

The National Institute of Mental Health (NIMH) has also been studying ketamine. One of the institute's researchers told NPR the effect was like looking at a tree with bare branches suddenly sprout healthy leaves. The NIMH recently tested ketamine on 30 human patients who suffered from depression. Brain scans revealed a similar increase in brainwave activity to the mice in Duman's study.

Unlike other antidepressants on the market, ketamine does not increase serotonin levels in the brain. Low serotonin has been shown to be one of the causes of depression. For most patients, antidepressants can take months to improve serotonin levels.

Instead, ketamine affects a substance called glutamate, a neurotransmitter found in the human brain and nervous system. Duman told the Hartford Courant that the drug creates a "robust impact" that can have an effect within hours, instead of weeks or months.

But Duman cautioned that the likelihood of ketamine becoming widely used as a depression treatment is unlikely because of its hallucinogenic side effects and the potential for abuse. Researchers are currently trying to create new drugs that would have the same antidepressant effect of ketamine without the high.